Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.65	11.601%	$103.3983	$103.40	$103.40	$103.40
Purchase #2	$247.56	7.246%	$265.4982	$265.50	$265.50	$265.50
Purchase #3	$36.27	12.837%	$40.926	$40.93	$40.95	$40.90
Purchase #4	$12.97	6.420%	$13.8027	$13.80	$13.80	$13.80
Purchase #5	$75.88	7.461%	$81.5414	$81.54	$81.55	$81.50
Purchase #6	$54.59	8.453%	$59.2045	$59.20	$59.20	$59.20
Purchase #7	$220.39	5.422%	$232.3395	$232.34	$232.35	$232.30
7 purchase totals =	$740.31		$796.7106	$796.71	$796.75	$796.60